The present invention relates generally to electrometallurgy and more particularly, it relates to electroslag remelting plants.
The invention may prove to be most advantageous for melting ingots by remelting a plurality of electrodes at one and the same time, with the number of the electrodes exceeding four and being divisible by two.
There are known in the art electroslag remelting installations wherein four and more electrodes coupled to a singlephase transformer are remelted at one and the same time. In order to achieve high performance characteristics of the remelting process, reduce power input per ton of the remelted metal and decrease the capacity of the single-phase transformer feeding the furnace, the electrodes are connected in series to the secondary winding of the above transformer. Half of the electrodes (one group) is connected to one end of the secondary winding of the transformer, the other half (another group) being connected to another end.
In the known plants, the electrodes in each group are disposed in a single row, side by side, with the electrode groups facing each other.
In melting in such installations an alternating current is made to pass nearer to the surface of the electrodes turned to the electrodes of an opposite polarity, i.e. internal surfaces of the electrodes facing the oppositepolarity electrodes are heated to a higher temperature than their external surfaces. Thus, in remelting the electrodes in magnetic steel, 200 mm thick, a drop in temperature along the electrode sections may reach 200.degree.C. With such a large temperature gradient the electrodes are liable to warp and a hazard may take place that the electrodes will touch a mould wall and, hence, burn it through. It is for this reason that in the above plants in order to exclude contact between the electrodes and the mould wall either the mould cross section is increased or the electrode section is reduced with a simultaneous enlargement of the electrode length and, hence, of the plant height. In these cases heat losses as well as power input per ton of the remelted metal are increased. Moreover, due to substantial heating of the electrode surfaces, the metal of the electrode surfaces is oxidized with the products of oxidation getting into slag and impairing the degree of refinement of the metal. When remelting the electrodes subject prior to the remelting operation to warping, which may always happen in practice, the electrodes of unlike polarity may be spaced out at different distances. In this case the electrodes placed on smaller spacing will upon melting be immersed in a slag bath to a smaller depth and those on larger spacings will be immersed in the slag bath to a larger depth during melting. The foregoing results in the formation of defects on the surface of the ingot obtained and adversely affects quality of metal.